Pedaling systems for transferring leg-driven power from the feet of a user to propulsion devices or exercise devices are well known. In most cases a circular drive sprocket gear is coupled by a chain to a driver sprocket gear, to rotate the rear wheel of a bicycle or to rotate a flywheel in an exercise device. Pedal cranks are located on each side of the drive sprocket gear, oriented 180.degree. apart from one another. Thus, by means of a circular reciprocating motion, the user of the device rotates the drive sprocket. Other applications, however, include simple devices such as recreational paddle boats and miniature cars and tractors employed as toys for small children.
In some cases, the circular reciprocating motion imparted by the feet of the user to the pedals is linked by means of elongated levers operated from axle offsets at the drive end of the device and coupled to comparable offset axle connections for driven wheels. The driving motion, however, is the same. The pedal cranks rotate about a fixed axis or center line, around which either a sprocket wheel or the drive lever offsets are rotated to produce the driving power to move the device forward.
In the case of bicycles, additional enhancements, which in no way affect the manner in which the original power is applied, include derailleur sets and multiple gears for enabling adjustment of the energy input required to rotate the rear wheel. These mechanisms, however, do not in any way alter the circular path which is followed by the pedals on the ends of the offset cranks which are used to rotate the basic drive member, whether it is a sprocket wheel or some other rotating device from which the input power is derived for application to an output-driven wheel or the like.
Exercise machines, which employ a similar type of action, have been developed in an effort to simulate the motions a person goes through in climbing stairs. Stair climbing machines typically have a pair of side-by-side "steps", which are alternately negotiated by the right and left feet, respectively, of a user. The force required to press down the step on one side, is employed, in part, to raise the step on the other side; so that as a person goes through the alternating left and right stepping sequence, differing amounts of energy are expended in accordance with the setting of the machine resistance to provide the desired exercise. Typically, the two "steps" are coupled to some type of a resistive flywheel to provide the level of resistance desired by the person using the device. In such stair climbing machines, however, the actual motion which normally is employed by a person in climbing up an actual set of stairs is not attained. In fact, the up and down motion which is applied is more akin to the movement which would be undertaken if a person were to walk down a set of stairs backwards. It is not the normal elliptical motion, which a person climbing a conventional set of stairs undergoes with each foot/leg motion operating in alternation.
Variable transmissions located between the pedal input of a bicycle and the output sprocket or wheel, without using a conventional derailleur device, are described in the U.S. patents to Kazuta U.S. Pat. No. 4,800,768 and Irwin U.S. Pat. No. 5,099,706. In both of these patents, however, the pedal path which is employed is a conventional circular path. Both of the patents describe a variable transmission, which uses two mutually perpendicular racks moved by a pinion coupled to the pedal shaft. In the devices of both of these patents the pinion only engages one of the racks on one side at a time, except for a brief time of transition from one rack to the next one in sequence. In the operation of the transmission devices of these patents, the racks are not continually moved by the pinion; and they are not engaged simultaneously, with the exception of the brief transition time mentioned.
It should be noted that a circular pedaling motion, particularly as applied to a bicycle, is highly inefficient. Maximum power is attained if the leg moves in a generally linear direction as it is pressed downwardly from the hip. When a circular motion is employed, as in the case of a conventional circular pedaling arrangement used on bicycles, some of the available power or force is dissipated in the first several degrees and the last several degrees of the full 180.degree. power movement from a position nearest the body of the user to a fully extended position, just prior to the return stroke or lifting of the leg. Consequently, if a more efficient pedaling path utilizing a more nearly linear stroke, as opposed to circular, can be devised, a greater amount of useful energy can be employed to rotate a drive wheel of a bicycle or other device. In addition, if an elliptical motion can be imparted to the operation of a stair climbing machine or the like, a more natural exercise of muscles can be attained, since such a motion more nearly simulates the actual motion encountered during climbing of conventional stairs.
It is an object of this invention to provide an elliptical path pedaling system, which overcomes the disadvantages of the prior art noted above, which is effective in operation, is easy to use, and is capable of adaptation into a variety of different devices.